The park includes one of the largest sections of untouched forest in southern Sweden1. Of the total park area (20 km2) more than half may be regarded as primeval forest, mostly in the western part of the park2. The park is in the transitional zone (“hemiboreal” 3) between the temperate deciduous forests and the boreal forests but so close to the northern limit of the zone that the vegetation is overwhelmingly boreal in nature. A large proportion of the primeval forest is of low productivity – low open Pinus sylvestris (Scots pine) forest on rocky terrain – a fact that has probably contributed to the preservation of the primeval forest next to the capital of Sweden. In the valleys, there are productive relatively tall standsdominated byPicea abies (Norway spruce). The other most common trees are also typical boreal species: Betula pendula (silver birch), B. pubescens (downy birch) and Populus tremula (common aspen). Alnus glutinosa (black alder) is common on moist sites. Quercus robur (pedunculate oak), pointing to the temperate zone, can be found here and there. Tree species diversity is low and most species are easy to identify. Old P. sylvestris trees are plentiful, the oldest being more than 500 years old 1. In 1999, a wildfire burned around 4.5 km2 of forest in the central part of the park2.

The park is located at an elevation of approx. 20–80 metres. Annual precipitation is approx. 510 mm and average annual temperature 6.9°C. The park is surrounded by Tyresta Nature Reserve, which serves as a buffer zone for the park1. There are a lot of marked hiking trails. Off-trail hiking is quite easy, though there are some low cliffs and small bogs. Camping is only allowed at designated sites2.